While moving through the world, smooth pursuit eye movements are used to maintain fixation on objects of interest. These eye movements can distort the visual motion on the retina thereby complicating visual motion processing. How is spatial orientation maintained during eye movements, and how do we control these pursuit movements in complex visual scenes? Cortical area MST is thought to be implicated in both of these processes because it is known to contain neurons which are activated by large-field visual motion from self-movement (optic flow) and by pursuit eye movements. We now propose to record single neuron activity in area MST of monkeys performing a pursuit task during the presentation of visually simulated, and/or real translational, self-motion stimuli. Three aims will be to 1) determine whether the individual neurons are activated both by smooth pursuit and optic flow, 2) characterize the role of retinal and extraretinal signals in these responses, and 3) examine the impact of real translational observer movement (vestibular and somatosensory) on these mechanisms. These experiments will bear on issues of sensorimotor integration for spatial orientation in naturalistic circumstances.